The present invention is directed to a vehicle suspension and particularly to a vehicle suspension adapted for the vocational vehicle market. The invention reduces the manufacturing cost and overall system weight of vehicle suspensions.
FIG. 1 illustrates a known vehicle suspension designated 20 designed to support vehicle frame rails (not shown) positioned on opposite sides of a vehicle center line in spaced relation above vehicle axles (not shown) of a tandem axle configuration for the vehicle. It will be appreciated that vehicle suspension components positioned on one side of the vehicle to support the vehicle frame rail of that side above its adjacent ends of the axles are duplicated on the other side of the vehicle to support the opposite vehicle frame rail above the opposite ends of the vehicle axles.
Vehicle suspension 20 includes an equalizing beam 22 extending longitudinally between the ends of the axles on a particular side of the vehicle. Equalizing beam 22 is connected to a vehicle frame rail bracket 24 by way of, among other things, bolster springs 26.
In this known vehicle suspension 20, the bolster springs 26 are positioned coincident with the wind up center of equalizing beam 22 to eliminate axle load transfer during braking and acceleration of the vehicle. In this arrangement, the bolster springs 26 are positioned inboard of the centerline of equalizing beam 22. This positioning of the bolster springs 26 creates a moment imbalance, which necessitates the use of a cross tube 28 to resist the moment forces.
Cross tube 28 extends laterally between the equalizing beams 22 positioned on opposite sides of the vehicle. The use of this cross tube increases manufacturing cost and overall system weight of the vehicle suspension. Additionally, use of this vehicle suspension requires an equalizing beam 22 that is unduly large and heavy, thereby translating into additional cost of the vehicle suspension, and in the case of commercial vehicles, reducing payload capacity.
FIG. 2 illustrates another prior vehicle suspension generally designated 30 designed to eliminate the shortcomings of the vehicle suspension 20 shown in FIG. 1, particularly those shortcomings that result from the moment imbalance due to the position of the bolster springs thereof. For the vehicle suspension 30, its bolster springs 32 are positioned above the equalizing beam 34 in a manner such that they are symmetrically positioned with respect to the vertical plane extending longitudinally through the center line of the equalizing beam. In other words, the bolster springs 32 are symmetrically inboard and outboard of the beam, thereby eliminating the requirement of a cross tube.
By positioning the bolster springs 32 vertically above the equalizing beam 34, however, the suspension 30 couples the vertical and articulation motions with the fore-and-aft motion. This coupling creates axle load transfer under braking and acceleration. It also reduces vehicle ride comfort.
One unique feature of the suspension disclosed herein is the repositioning of rubber bolster springs for performance and enhancement. The bolster spring pairs are positioned about a suspension walking beam on opposite sides thereof. This permits the uncoupling of the articulation and vertical motions of a walking beam suspension from the induced fore/aft motion by repositioning the rubber bolster springs coincident with the windup center of the walking beam. It also eliminates the necessity of a cross tube, further reducing cost and weight from the suspension system.
The use of split bolster springs provides the benefit of the bolsters being coincident with the windup center of the beam without the penalty of either a cross tube to absorb the moment imbalance of inboard bolsters, or the penalty of an excessively large beam to span outside of the bolsters. The split bolster spring arrangement uncouples the vertical and articulation motions from induced fore/aft motions, resulting in improved vehicle braking and ride characteristics.
The split bolster arrangement allows the bolsters to be lowered to straddle the beam, thereby situating their line of action coincident with the beam centerline. This eliminates the fore/aft motion induced by vertical or articulation motion. Also, because the bolster pairs are symmetrically inboard and outboard of the beam, there is no moment imbalance and therefore no requirement for a cross tube.
The fundamental principle behind the inherent benefits of the split bolster configuration is the static equilibrium equation, (i.e., xcexa3M=0). By lowering the bolster line of action to the beam centerline, the moment arm has been reduced to zero, thus eliminating fore/aft motion. By positioning the bolster pair symmetrically straddling the beam, the resultant moment is zero.
The addition of molded-in studs for assembly reduces the width of the part, allowing the outboard bolster springs to be positioned alongside the beam without interference to the tire. This increases the quantity of rubber bolsters required per suspension resulting in improved economies of scale, thereby reducing unit cost. As a result, there is enhanced suspension articulation (increased range of motion) and ride quality.
Referring back to FIG. 2, the fabricated equalizing beam 34 of the vehicle suspension 30 illustrated therein includes two symmetric channeled sections 36, 38 that must be projection-welded together at a center weld 40. The projection-welding process requires a special set up and often suffers from a blow-through condition in production. The center weld is discontinuous and positioned on the bottom side of fabricated equalizing beam 34, which can result in stresses that may contribute to tensile load conditions. The center weld also makes it difficult, if not impossible, to attach brackets on beam 34 at a center location thereof. As shown, the bolster springs 32 are connected to the equalizing beam 34 by downwardly extending brackets positioned on longitudinally opposite sides of center weld 40.
Another unique feature of the disclosed suspension is that a fabricated walking beam is designed in a simplified manner to eliminate weld complexity. In the fabricated beam, fewer components and improved weld conditions are present. The main channel is formed by a U-shaped one piece structure, rather than the two piece design used in conventional fabricated beams. This results in a continuous weld condition on the top surface of beam, eliminating the need for the discontinuous center weld, which is often difficult to produce. Additionally, a simple fabricated bracket has been attached to the walls of the main channel on both the inboard and outboard walls to permit mounting of the split pair bolster spring assembly. Because this simple bracket design is common to both sides of the beam, it eliminates part complexity.
The fabricated beam reduces actual welding time, in addition to the number of setups, and time required for each setup. In addition, the positioning of the weld at the top of the beam permits the weld to work in compression rather than tension, providing greater durability.
The fabricated beam eliminates the need for a center weld, thereby improving the inherent strength of the beam and improving manufacturability. Positioning of the welds at the top of the beam places the welding in a compression load condition, making it an inherently durable structure.
With regard to the fabricated beam, there is a reduced number of components. It is also reduced weight (improved design optimization). Also, the designed xe2x80x9cracetrackxe2x80x9d feature on the A-shaped side brackets improves welding over prior art beams.
With prior vehicle suspensions, a different saddle must be maintained for use on each particular vehicle frame configuration. This requires a unique saddle to be designed, developed, maintained and stored for each unique vehicle frame configuration. It will be appreciated by those skilled in the art that this enduring problem has increased the costs associated with the manufacture and service of vehicle suspensions.
Another unique feature of the vehicle suspension disclosed herein is that a modular shear (attachment) plate connects the saddle to the vehicle frame rail. As a result, multiple vehicle frame configurations (i.e., ride heights and frame widths) can be absorbed through modifications to the hole/bore positions machined through the shear plate, permitting production of a uniform, universal saddle. This results in reduced inventory of saddle subassemblies.
The modular shear plate design permits compatibility to any industry standard frame configuration with the replacement of an interchangeable attachment part. This shear (or attachment) plate also simplifies the components that must be maintained in inventory. The modular attachment (shear) plate simplifies assembly and reduces component inventory.
The modular shear/attachment plate allows for a universal saddle subassembly that can be sized and adapted for all truck frame configurations. As a result, a single main saddle subassembly can be used for all truck frame configurations. Various attachment plates will be used for each particularly different truck frame configuration. With respect to the shear plate, it reduces the fabricated component complexity, reduces the length of the weld translating into lower production costs, and allows for fewer weld setup fixtures and station requirements, translating into lower tooling investment costs.
The above-noted and other desired benefits of the preferred form of the invention will be apparent from the following description. It will be understood, however, that a system or embody could still appropriate the claimed invention without accomplishing each and every one of the desired benefits, including those gleaned from the following description. The appended claims, not these desired benefits, define the subject matter of the invention. Any and all benefits are derived from the preferred form of the invention, not necessarily the invention in general.
In a preferred embodiment, the present invention is directed to a vehicle suspension for supporting a longitudinally extending vehicle frame rail above the adjacent ends of tandem axles. The suspension includes a longitudinally extending equalizing beam connected to each such end of the tandem axles. First and second bolster springs are mounted to and straddle the equalizing beam. The first bolster spring is positioned outboard of the equalizing beam. The second bolster spring is positioned inboard of the equalizing beam. Third and fourth bolster springs are mounted to and straddle the equalizing beam. The third and fourth bolster springs are positioned forward of the first and second bolster springs. The third bolster spring is positioned outboard of the equalizing beam. The fourth bolster spring is positioned inboard of the equalizing beam. Most preferably, the bolster springs are positioned coincident with the wind up center of the equalizing beam.
In the preferred embodiment, A saddle is mounted to the bolster springs. An attachment plate is mounted to the saddle and to the vehicle frame rail.
With respect to the equalizing beam, it preferably includes a longitudinally extending U-shaped main channel and a longitudinally extending top plate. The main channel and top plate are welded together along the top of the equalizing beam.
With respect to the attachment plate, it preferably includes a mounting surface that is designed to have bores machined through it. The mounting surface is configured such that the bores can be machined through it at a variety of positions and the saddle can be used with a variety of vehicle frame rail configurations.